ABSTRACT
Two types of alpha-globin variants were found in 0.2% of a large number of newborn from Malta. The two hemoglobins were identified from tryptic maps on a Vydac C18 column and by alpha-globin gene sequencing as Hb St. Luke's (isoelectric point = 7.18+/-0.017) and Hb Setif (isoelectric point = 7.26+/-0.010). Hb St. Luke's [alpha95(G2)Pro-->Arg] was found to result from a C-->G mutation at the second position of codon 95 on an alpha1-globin gene, and Hb Setif [alpha94(G1) Asp-->Tyr] resulted from a G-->T mutation at the first position of codon 94 on an alpha2-globin gene. Quantification of Hb St. Luke's (11.1+/-1.12%) and Hb Setif (14.7+/-2.22%) in peripheral blood hemolysates indicated that, in the absence of either an alpha- or a beta-thalassemia allele, the protein products of the alpha1- and alpha2-globin genes were nearly equal in quantity.
Subject(s)
Globins/genetics , Hemoglobins, Abnormal/genetics , Point Mutation , Arginine/genetics , Aspartic Acid/genetics , Female , Humans , Male , Malta , Proline/genetics , Tyrosine/geneticsSubject(s)
Factor VII Deficiency/genetics , Factor VII/genetics , Alleles , Amino Acid Substitution , Child, Preschool , DNA/chemistry , DNA/genetics , DNA Mutational Analysis , Factor VII/metabolism , Family Health , Female , Genotype , Humans , Male , Mutation, Missense , Pedigree , Point MutationABSTRACT
In vitro DNA amplification and dot blot analysis with synthetic allele specific oligonucleotides (ASO) identified the beta + IVS, I-6 (T --> C) thalassaemia in 78% of 32 chromosomes from 16 beta-thalassaemia homozygotes in Malta. The preponderance of a single thalassaemia mutation in one population is unusual. The beta + IVS, I-6C thalassaemia mutation was also found in three carriers who had an associated beta globin heterozygosity, i.e. Hb Valletta (or alpha 2 beta 2 87PRO) or Hb S (or alpha 2 beta 2 6VAL). The proportion of Hb A in these cases (av. = 29.7%) provided objective documentation of the relatively mild effect of this mutation on in vivo globin gene expression. However, the expression of homozygous disease was more severe in developing children compared to adults. The beta + IVS, I-6C mutation complicates population testing because heterozygotes can have Hb A2 levels below those classically associated with beta thalassaemia.
